TrickySomething that is a little difficult or requires special care or skill is tricky. A person is tricky when they often lie but not about very serious things, or know a lot of small, dishonest ways to get what they want from other people.
EX: Sarah's house is nearby, but getting there can be a bit tricky. You have to go up this street here, turn left onto the High Street, then right immediately onto York Road and follow it to the end. Her building is behind the corner shop there.
EX: Denis is really fun to drink with, he's great at telling jokes and stories, but he can be a bit tricky. He's pretty skilled at disappearing before the bill comes.
If something requires a special skill, or a certain action that is not clear until someone shows you how to do it, it has a trick to it. The special skill or action is the trick. And to express the idea that it's very difficult to change old habits or to learn new skills, we often say you can't teach an old dog new tricks.
EX: Gigi's apartment is really nice, but the lock on the old door is difficult to open and close. It definitely has a trick to it—you have to pull it up as you put the key in, or else it gets stuck inside.
EX: I really want to get up early in the morning and go to the gym before work, but I just can't get into the habit. I guess you can't teach an old dog new tricks. I'll just keep going at night.